JPH06103690A - Magnetic disk device - Google Patents

Abstract

PURPOSE:To provide the magnetic disk device which does not contaminate a disk, maintains an always sealing function and has good assembly quality. CONSTITUTION:A spindle 8 is fixed and integrated to the end of a hub 6 for mounting a magnetic disk 10 to constitute a rotating body. A housing 4 disposed on the inner side of a hub 6 is provided with a bearing and the spindle 8 is inserted therein, by which the spindle is freely rotatably supported. A thrust bearing 13 is disposed at the spindle end and one end thereof is provided with a sealing device 14. To this sealing device 14, a pair of pole piece 15 formed of magnetic materials to a shaft by means, such as press fitting, adhering, and a magnet 17 magnetized in the axial direction to the inner peripheral part of the hub facing the pole piece 15 are mounted. A magnetic circuit is constituted between the pole piece 15 and the magnet 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle unit such as a magnetic disk device, an optical disk device or a laser beam printer, and more particularly to a seal device suitable for preventing the disk or mirror from being contaminated.

[0002]

2. Description of the Related Art Generally, in a rotating device such as a magnetic disk device or an optical disk device which is extremely reluctant to contaminate a disk, a seal device for preventing the lubricant of the bearing from scattering is provided on the end surface of the bearing. In addition, a magnetic fluid seal is often used as the sealing method. Incidentally, with the recent downsizing of computers, there has been a demand for higher speed and higher recording density of magnetic disk devices. Therefore, the speed of the magnetic disk spindle unit is increased, and the magnetic fluid may be scattered by the centrifugal force along with the scattering of the lubricant as the number of rotations increases, and the reliability of the magnetic fluid sealing device itself becomes a problem. . Conventional magnetic fluid seal devices are disclosed in Japanese Patent Laid-Open Nos. 60-175870 and 60
As disclosed in Japanese Patent No. 245878, a compact seal is provided by providing a multi-stage pole piece on a shaft, arranging a permanent magnet and a magnetic pole piece on the stationary side, and forming a magnetic circuit with a ball bearing and a magnetic pole piece. We provide equipment. In addition, JP-A-60-249727, JP-A-64-79420 and JP-A-64-725.
As disclosed in Japanese Utility Model Publication No. 1-87330 and Japanese Utility Model Laid-Open No. 1-87330, there is also one in which a magnet and a pole piece are arranged on an outer ring or an inner ring of a ball bearing to form a sealing device. Further, as disclosed in USP No. 4630943, there is another one in which a magnet and a pole piece are provided on the stationary side on the inner peripheral side of the bearing diameter to improve the sealing function. Further, as disclosed in Japanese Utility Model Laid-Open No. 63-42928,
A structure has been devised in which a protrusion is provided on the shaft side, a magnet and a pole piece are arranged on the stationary side, and magnetic fluid is less likely to scatter due to centrifugal force. On the other hand, as disclosed in Japanese Utility Model Laid-Open No. 64-54748, there is also a structure in which a cover for preventing magnetic fluid from scattering is attached to the outer periphery of the pole piece.

[0003]

The above-mentioned prior art is disclosed, for example, in JP-A-60-175870 and JP-A-60-245878, in which the magnetic fluid is attracted to the magnet when the magnetic fluid scatters during high-speed rotation. Difficult to collect in a pole piece. In addition, JP-A-60-249727 and JP-A-64-7942
No. 0, Japanese Utility Model Laid-Open No. 64-725 and Japanese Utility Model Laid-Open No. 1-87330 do not consider the dispersion of magnetic fluid. on the other hand,
In Japanese Utility Model Laid-Open No. 64-54748, a magnetic fluid scattering prevention cover is provided, but the magnetic fluid collected by the scattering prevention cover is only retained on the side of the pole piece.
Hard to be collected in the seal gap at the tip of the pole piece. Even in a structure in which magnetic fluid is unlikely to scatter due to centrifugal force as in Japanese Utility Model Laid-Open No. 63-42928, the magnetic field is held at a position where the magnetic flux density is low, so the seal withstand pressure is low, and consideration is given to axial scattering. Didn't.

The object of the present invention is to prevent the magnetic fluid from scattering due to centrifugal force at the time of high-speed rotation, and to construct a sealing device capable of immediately recovering the magnetic fluid even if the magnetic fluid scatters, thereby contaminating the disk. It is to provide a magnetic disk device that can be prevented.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a housing arranged inside a hub in which a spindle is fixed to a hub end where a magnetic disk is mounted and integrated to form a rotating body. A bearing is provided, the spindle is inserted therein, and the spindle is rotatably supported. A thrust bearing is arranged at the end of the spindle and a sealing device is provided at one end thereof. According to the structure of the sealing device, a pair of pole pieces formed of a magnetic material are attached to the shaft by means such as press fitting or adhesion, and an axially magnetized magnet is attached to the inner peripheral portion of the hub facing the pole pieces. A magnetic circuit is constructed between the pole piece and the magnet. Further, both end portions and the outer peripheral portion of the permanent magnet are covered with non-magnetic rings, and the inner diameters of the non-magnetic rings at both end portions of the magnet are made smaller than the outer diameter of the pole piece.

[0006]

The magnetic disk device according to the present invention is constructed in this way, and when the spindle equipped with the magnetic disk rotates, the temperature inside the housing rises due to bearing loss, the internal pressure rises, and the lubricant begins to evaporate. .
The magnetic fluid seal counters these increases in internal pressure and prevents foreign matter such as lubricant vapor or abrasion powder from contaminating the disk surface. However, as the speed of the magnetic disk device increases, the peripheral speed of the seal gap portion of the magnetic fluid seal also increases,
The centrifugal force applied to the magnetic fluid also increases. Due to this increase in centrifugal force, when the centrifugal force exceeds the holding force of the magnetic fluid, the magnetic fluid scatters in the tangential direction of the outer diameter of the pole piece. Therefore, if there is a strong magnetic field in the direction in which the magnetic fluid scatters, the magnetic fluid will be captured by this magnetic field and will not flow out. In the structure of the present invention, since the magnet is arranged at a position facing the pole piece attached to the shaft,
Even if the magnetic fluid is scattered by the centrifugal force, there is a magnet in the scattering direction, and the magnetic fluid is captured by the magnet. Moreover, since the rings formed of a non-magnetic material are attached to both ends and the outer peripheral portion of the magnet, there is no leakage magnetic flux, and the cover ring does not flow out.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a vertical sectional view of a magnetic disk device according to an embodiment of the present invention. FIG. 2 is an enlarged partial sectional view of the sealing device portion of FIG. In assembly, the two sealed covers 1 and 2 are integrally assembled, and the end portion of the bearing housing 4 is fixed to the lower base plate 3 fixed to the sealed cover 2. A motor stator 5 is attached to a central portion of the bearing housing 4 in the axial direction, and a motor is constituted by the stator 5 and a rotor magnet 7 attached to the inner peripheral portion of the hub 6 so as to face the stator 5. A spindle 8 is press-fitted and fixed to the end of the hub 6. A plurality of magnetic disks 10 are mounted on the outer circumference of the hub 6 via spacer rings 9, and are fastened by a clamp 11 fixed to the upper end of the hub 6.

On the other hand, a radial bearing 12a is provided on the open end side of the bearing housing 4 and a sealing device 14 is provided on the upper end of the radial bearing.
However, a radial bearing 12b and a thrust bearing 13 are arranged on the sealed end side to support the spindle 8.

The sealing device 14 will be described in detail with reference to FIG. A pole piece 15 fixed to the spindle 8 by press fitting or adhesion, a magnet housing 16 attached to the upper end of the bearing housing 4, a magnet 17 fixed to the magnet housing, a cover ring 18 attached to the upper end of the magnet 17, and a magnetic fluid 19. It is composed by. Among these components, the pole piece 15 is made of a magnetic material, and the magnet housing 16 and the cover ring 18 are made of a non-magnetic material.
The magnet 17 is arranged at a position facing the pole piece 15 and is magnetized in the axial direction. Therefore, a magnetic circuit is formed between the pole piece 15 and the magnet 17 as indicated by the alternate long and short dash line.
The magnetic fluid 19 is retained in the seal gap between the permanent magnet 17 and the permanent magnet 17, and the function as the seal device is maintained.

Next, the effect of preventing the magnetic fluid from scattering during high-speed rotation of the present invention will be described with reference to FIG. FIG. 3 is a perspective view of the sealing device in which the spindle 8 is omitted. The pole piece 15 starts to rotate at high speed, and the magnetic fluid 1
When the centrifugal force exceeds the holding force of No. 9, it is blown in the tangential direction of the outer diameter portion of the pole piece 15 shown by the arrow in the figure. At this time, in the sealing device according to the present invention, since the magnetic poles of the magnet are in the direction in which the magnetic fluid 19 is scattered, they are captured by the magnet. Moreover, since the cover ring 18 formed of a non-magnetic material is installed on the upper end surface of the magnet, and the inner diameter of the cover ring 18 is formed smaller than the outer diameter of the pole piece 15, the scattered magnetic fluid must be contained. It is collected by the magnet 17.

Further, the magnetic disk device may be vibrated during transportation or the like, and the magnetic fluid may flow due to the vibration. At this time, since the pole piece 15 is made of a magnetic material and a magnetic circuit is formed, magnetic fluid adheres to the side surface of the pole piece 15 and may be scattered by centrifugal force when the magnetic disk starts to rotate. is there. To solve this problem, as shown in FIG. 4, magnetic shield rings 20 made of a non-magnetic material are fixed to both end faces of the pole piece 15 by adhesion or the like. As a result, no magnetic circuit is formed on the side surface of the pole piece 15, so that the magnetic fluid 1
9 does not adhere to the side surface of the pole piece 15, so that the magnetic fluid can be prevented from flowing out due to the vibration force during transportation.

Next, another embodiment according to the present invention is shown in FIG. This embodiment is almost the same as the embodiment, and the difference from the embodiment is that the inner diameter of the cover ring 18 is substantially the same as the inner diameter of the magnet 17. In the embodiment, the spindle 8
The hub 6 had to be press-fitted after assembling the bearing 12 and the seal device 14 in the above. However, in this embodiment, the hub 6 can be assembled after being press-fitted into the spindle 8 and thus assembled into the bearing housing 4. The processing accuracy is improved.

FIG. 6 is an enlarged view of the sealing device of FIG. In this embodiment, since the cover ring 18 and the magnet 17 have substantially the same diameter, the holding force against the scattering in the axial direction is slightly reduced. Therefore, it is necessary to increase the thickness of the cover ring as compared with the embodiment.

Also in the embodiment, the cover ring 1
If 8 is made of an elastic material such as rubber, the same effect as in this embodiment can be obtained.

[0015]

According to the present invention, by disposing a pole piece attached to a spindle and a magnet at a position facing the pole piece on a stationary side, even if a magnetic fluid scatters due to centrifugal force during high-speed rotation, scatters. Since the magnetic pole with a high magnetic flux density is present in the direction of the magnetic field, it is immediately captured and returns to its original state, so that the disk is not contaminated and the sealing function is always maintained, providing a magnetic disk device with good assemblability. can do.

[Brief description of drawings]

FIG. 1 is a sectional view of a magnetic disk device according to an embodiment of the present invention.

2 is an enlarged partial cross-sectional view of a sealing device portion of FIG.

FIG. 3 is an explanatory diagram showing the effect of the present invention.

FIG. 4 is a partial cross-sectional view showing an embodiment of the present invention.

FIG. 5 is a vertical cross-sectional view of a magnetic disk device according to another embodiment of the present invention.

6 is an enlarged partial cross-sectional view of a sealing device portion of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Upper sealing cover, 2 ... Lower sealing cover, 3 ... Base plate, 4 ... Bearing housing, 5 ... Motor stator, 6 ...
Hub, 7 ... Rotor magnet, 8 ... Spindle, 9 ... Spacer, 10 ... Disk, 11 ... Clamp, 12 ... Radial bearing, 13 ... Thrust bearing, 14 ... Sealing device, 1
5 ... Pole piece, 16 ... Magnet housing, 17
… Magnet, 18… Covering.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shoro Takatsuka 2880 Kunizu, Odawara, Kanagawa Stock company, Hitachi Ltd. Odawara factory (72) Inventor Osamu Beppu, 2880, Kozu, Odawara, Kanagawa Hitachi, Ltd. Odawara factory Within

Claims (4)

[Claims] 1. A hub for mounting a magnetic disk in which a plurality of magnetic disks are laminated via spacers, a spindle integrally formed with the hub, a motor for driving the spindle, and a bearing for supporting the spindle. In a spindle unit composed of a seal that prevents scattering of lubricating oil from the bearing, a pole piece made of a magnetic material is press-fitted or adhered to the spindle, and the pole piece is formed on the inner peripheral portion of the hub facing the pole piece. A magnetic disk device characterized in that a ring-shaped magnet magnetized in the axial direction is arranged and a seal device enclosing a magnetic fluid is incorporated. 2. The magnetic disk drive according to claim 1, wherein the open end and the outer peripheral portion of the magnet are covered with a non-magnetic material. 3. The magnetic disk drive according to claim 2, wherein the inner diameter of the cover ring made of the non-magnetic material at the open end of the magnet is smaller than the outer diameter of the pole piece. 4. The magnetic disk drive according to claim 2, wherein the cover ring made of the non-magnetic material is formed of an elastic body.